Fireplace insert structure



FIG. 1 is a perspective view of a fireplace insert structure showing my new design;

FIG. 2 is a top plan thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a front elevation thereof;

FIG. 5 is a right-side elevation thereof;

FIG. 6 is a left-hand elevation thereof; and

FIG. 7 is a rear view thereof.

FIG. 2-7 are drawn to the same scale, which scale is smaller than that employed in FIG. 1. 

The ornamental design of a fireplace insert structure, substantially as shown and described. 